Article Taken from "This Old House"
Written by LESLIE PLUMMER CLAGETT
If choosing a fan with wood blades, make sure they are sealed to prevent warpage. Fans rated for use in damp locations, such as a porch or bathroom, usually have plastic paddles. Because they're produced as factory-matched sets, you can't swap out blades from different fans; it throws them out of balance , but many manufacturers offer a variety of blade styles for a given fan, allowing you to customize the look. Many blades are also reversible, featuring different finishes on either side of the paddle. Take note of the pitch of the blades because that, along with the blade span, determines how well the fan cools. The steeper the blade pitch, the more effectively the fan will move air around. Look for angles between 11 and 16 degrees; this information is called out in the manufacturer's catalog or on the packaging. Smaller fans that are designed for tight quarters such as bathrooms, where circulating the air and exhausting it help to prevent mold and mildew from forming in the closed, often steamy space have blades canted up to 22 degrees. Fans that are to be used in damp or humid locations, like the bathroom or a covered porch, must be Underwriters Laboratories-certified for moist environments.
Motor. The motors in ceiling fans range between 1/60 and 1/3 hp. A higher-power motor helps meet the demands put on the fan by the resistance of the blades. In other words, the greater the span and pitch, the more powerful a motor is needed. Heavy-duty motors are more resistant to overheating, as well. A motor with sealed bearings that never need to be oiled is among the items that denote quality in a fan. Another is a rubber flywheel, which helps keep the torque under control, stabilizing the fan while preventing noise from channeling up into the ceiling, where it is amplified. Inexpensive fans often lack these noise-dampening components.